1. Field of the Invention
The present invention relates to a water base ink set for ink-jet recording and an ink-jet recording apparatus which accommodates the same.
2. Related Art
The printer technique based on the ink-jet recording system is the printing technique based on, for example, the bubble system in which an ink is discharged from a minute diameter nozzle by the aid of bubbles generated by rapid heating, or the piezoelectric system in which an ink is discharged from a minute diameter nozzle by using a piezoelectric device which is deformable in accordance with the voltage application. Inks, which have several colors respectively to serve as fundamental colors, are converted into minute droplets of several picoliters to several tens picoliters, and they are selectively landed on the paper surface to form an image thereby.
The ink-jet recording system is advantageous in that an image, which has color reproduction approximate to the full color and which has no granular texture, can be formed by highly accurately controlling the discharge of the minute droplets, and thus the high letter-printing quality and the high image-printing quality are obtained. Further, when a pigment is used as the coloring agent, it is also possible to reproduce a sharp edge equivalent to those obtained by a laser printer.
It is affirmed for the water base ink for ink-jet recording that the use of a black pigment as the coloring agent for the black ink is useful in order to reproduce a sharp edge, for example, when letters and ruled lines are printed. It is also affirmed that the use of a dye as the coloring agent for the color ink is useful in order to form a colorful and vivid image such as a photograph. However, when the black ink, in which the black pigment is used as the coloring agent, is used in combination with the color ink in which the dye is used as the coloring agent, then the dispersion state of the black ink dispersed in the black ink becomes unstable due to the contact between the black ink and the color ink, and any aggregation is caused in some cases. The ink-jet recording system is based on such a mechanism that the ink is discharged highly accurately from the nozzle having the minute diameter. Therefore, the following problem has been hitherto caused. That is, if the aggregation occurs in the vicinity of the nozzle, the nozzle is clogged to cause any serious deterioration of the printing quality including, for example, the discharge curvature and the discharge failure of the ink. Further, the following problem has been hitherto caused as well. That is, if the aggregation occurs in a suction pump for the maintenance, the pump malfunctions.